Accelerate at 2/3rd throttle, change up at low rpm, coast at half throttle once in top gear. When you get to 0.1L remaining, let off throttle completely and rollto a stopuntil the timer expires. Then hit the accelerator to use the last drop of fuel.
It's probably easier to gold with a manual but I did it with a automatic. You just have to experiment.What is the theory to gold the eco challenges?